Substituted methylene diphosphonic acids and their salts



Unite Sta s Patent ABSTRACT OF THE DISCLOSURE i Benzyl and carboxymethyl Substituted methylene diphosphonic acids and their water-soluble salts as novel compounds useful as detergency builder salts.

This patent application is a continuation-in-part of a copending application, Serial No. 266,055, filed March 18, 1963.

This invention relates to a novel class of compounds. More particularly, this invention relates to substituted methylene diphosphonic acid compounds and their water soluble salts, which possess valuable detergency builder properties with a broad range of detergent compounds. Novel laundering compositions whose cleaning powers are enhanced by these novel compounds are also described.

The use of builders are adjuncts to soap and synthetic detergents, and the property which some materials have of improving detergency levels of such detergent compounds is well known.

An ever increasing interest in builder materials because of their valuable properties in detergent formulations has resulted in the development of many candidates as builder materials. This increased interest has focused attention upon thened for improved building and new chemical compounds which possess significant builder properties.

It is, therefore, a primary object of this invention to provide a novel class of substituted methylenediphosphonic acid compounds and their salts.

Still further objects and the entire scope of applicability of the present invention will become apparent from'the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention; are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent from this detailed description to those skilled in the art.

According to this invention, the new class of substituted methylenediphosphonic acid compounds has the following general formula:

.monium"(e.g. triethanol ammonium) salt form of the above novel acids' 'ca'nbe prepared according to this invention. The alkali metal derivatives are the preferred compounds. Suitable alkali metals include sodium and potassium. The compounds herein are preferably obtained as the tetrasodium and trisodium salts as prepared according to this invention. The lesser neutralized forms such as monosodium and disodium derivatives or the free acid form are readily prepared also. They too have builder properties comparable to the trisodium and tetrasodium salt forms, provided, that additional alkali is added to adjust the pH of the washing solution to be within a range of from about 8 to about 12. The standard alkaline materials can be used for this purpose, such as alkali metal silicates, phosphates, borates and carbonates. Free alkali materials such as sodium and potassium hydroxides can be used also.

Specific illustrations of the newly discovered compounds include the following alkali metal derivatives. The trisodium salt is exemplified but, of course, other alkali metal and water soluble salts such as those mentioned above are within the scope of this invention.

(1) trisodium benzyl-methylenediphosphonate,

CGH5CHZCH (PO Na (2) trisodium bis(benzyl)-methylenediphosphonate,

( 6 5 2)2 a z) Qs (3 tetrasodium- (carboxymethyl -methylenediphosphonate, NaO CCH- CH(PO Na (PO NaH) (4) pentasodium-bis(carboxymethyl) methylene diphosphonate, (NaO CCH C(PO Na (PO NaH) viously unkno'wn class of compounds. The members of this class have many uses besides the valuable builder applications described above. For instance, they can serve as valuable intermediatesin the production of other compounds'such as phosphine oxide derivatives which are known surface active materials. Moreover, phosphine oxides made from the compounds of this invention can be used as recovery agents for uranium.

The claimed diphosphonates have been found to be useful as sequestrants. This utility is indicated by the following table, wherein tworepresentative members of the claimed class of compounds, trisodium benzyl methylenediphosphonate and tetrasodium-(carboxymethyl)- methylenediphosphonate, are compared to tetrasodium pyrosphate (Na P O and sodium tripolyphosphate (Na P O The testing was done using the method of Irani and Callis, The Journal of Physical Chemistry, vol. 64, 1398 (1960), with caprate substituted for oxylate It will be noted that the performance of these members of the present invention is unexpectedly high at higher pH levels, e.g. 11 and 12. The values for tetrasodium- (carboxymethyl)-methylenediphosphonate in Table I are especially significant and noteworthy.

More especially, however, water soluble derivatives of the new compounds of this invention surprisingly have been discovered to be highly efiicient detergency builders. They ofler as an advantage over previously known builder compounds the possibility of using proportionally smaller amounts of builder compound without sacrificing ing over-all cleaning performance. Other similarly valuable advantages are discussed hereinafter.

Synthesis routes of these novel compounds essentially involve, as a first step, an oxidation-reduction type of a reaction between a metallating agent such as sodium, sodium hydride, potassium or potassium-sodium eutectic alloy, and a tetraalkyl ester of methylenediphosphonic acid. This reaction is highly exothermic and it is essential that it be conducted at low temperatures on the order of C. to 35 C., and preferably between 15 C. and 30 C. The reaction product is a carbanion derived from the active methylene grouping present in the parent methylene ester starting material. The equation for this step is as follows:

This carbanion reaction product is then reacted with a suitable alkylating agent in order to obtain the desired substituted methylenediphosphonate tetraalkyl ester.

The phosphonate esters so derived can usually be purified by simple distillative means, if desired, after removal of by-product salts. More often, the crude product is converted directly to the free phosphonic acid by methods known to those skilled in the art, namely, by hydrolyzing with concentrated hydrochloric acid or in the case of isopropyl esters, by pyrolysis. An excellent novel pyrolytic process is described in a copending application Serial No. 218,863, filed August 23, 1962, by Clarence H. Roy and now abandoned. Addition of base such as sodium hydroxide and potassium hydroxide to the acids results in formation of the corresponding salts.

The tetraalkyl ester of methylenediphosphonic acid used as a starting material-for preparing the novel compounds of this invention can beprepared acc ding to the following method. Preparation of tetraisopropyl methylenediphosphonate 624.7 gm. of triisopropyl phosphite (3 moles, 681 ml.) and 173.9 gm. of dibromomethane (1 mole, 70 ml.) were combined in a reaction apparatus composedpf; a .1'-liter, 3-neck flask fitted witha magneticstirrer, {a thermometer, and a fractionating column for separating 'the isopropy l bromide by-pro'duct from the refluxing mixtureiThe fi"actionating column was constructed from as36-in'chfLiebig condenser that had been. modified, to accommodate Awinch glass helices as packing. A Barrett distilling..-receiver, which had been modified by the addition of a thermometer well and thermometer was connected to the top of the fractionating -column{ and to the top of the Barrett receiver was fitted a Dewar condenser cooled with Dry Ice and protected from atmosphericmoisture by a drying tube. The temperature of the reactionmixture was quickly brought to reflux at 143 C. The temperature'of the circulating water in the packed reflux condenser was maintained at 65 C. This temperature was suflicient to return unreacted starting material and allow the byproduct isopropyl bromide to be distilled. The heat input to the reaction was such that vigorous refluxing continued as the temperature of the mixture slowly' increased. After about two hours of heating the first distillate .was observed, and after five hours a total of'33 gm. of isopropyl bromide had been collected. The temperature of the reaction mixture was allowed to increase to 185 C. over a twelve hour period, and by means of an electronic temperature controller it was held there for the remainer of the reaction.

After approximately 16 hours, the reaction was essentially complete as judged by the yield of isopropyl bromide, 231 gm. which represented a yield of about 92%. Further heating served no useful purpose, although re action times of 20 hours were employed on occasion. I

When the reaction was complete, the reaction mixture was transferred to a distilling flask and the low boiling materials (excess phosphite, etc.)'were removed through a short one-piece still under a vacuum of 0.1 mm. of mercury and head temperatures up to 50 C. At this point the contents of the flask weighed approximately 330gm. and was 93% to 95% tetraisopropyl methylenediphosphonate. The purity of this material was suflicient to proceed in the synthesis of the novel compounds of this invention.

If a purer product is desired, a high capacity vacuum pump can be introduced into the system and the pressure reduced to 0.005 mm. of mercury. The material boiling between C. and 116 C. is collected and redistilled through an electrically heated 24-inch Vigreux column. A complete example of this type' of process is presented in a :copending patent application, Serial No. 218,862, filed August 23, 1962, by Clarence H. Roy and now Patent No. 3,251,907.

In the preparation of the tetraalkyl ester reactant, particular care must be'taken to 'insurethat the starting materials are pure and freshly distilled because the presence of acidic residues in the product causes premature decomposition upon attempted distillation. If this occurs, the product must be neutralized at once, whereupon distillation may be resumed; The neutralization is time consuming and laborious, and is 'notrecommended as an alternative to initial purification of reactants.

It should be noted that a product obtained by fractionation through a Vigreux columrris .very nearly aspurc as that obtained by careful fractionationthr'ough a 24-inch spinning band column; also the yield is muchirnproved because the faster through put reduces heating ,timejand consequently, reduces theamountpf undistillable resinous residues. The resinous residue in the [flask should not be discarded, however, .becausehydr olysis;ofthisifiziteriril will yield methylenediphosphonic acid of-remarkable purity. 5

. The tetraalkyl methylenediphosphonate compound prepared according to the process just described or the process described in the copending application noted above can be used in this invention as illustrated in the following examples.

EXAMPLE I (A) Preparation of tetraisopropyl benzylmethylenediphosphonate Sodium, 16.09 gm. (0.7 mole), was dispersed in 150 ml. of boiling toluene contained in a one liter, three-neck flask which fitted with a thermometer, a 50 ml. oflset, additive type separatoryfunnel, an Allihn condenser, and a high speed stirrer. The dispersion was cooled to. 20 C. and 241.8 gm. (0.7 mole) tetraisopropyl methylenediphosphonate, of CH2[PO(OC3H7-i)2]2, was added dropwise at a rate such that the reaction temperature could'be controlled and maintained at 25 C.30 C. by external cooling with a Dry Ice bath. When this reaction had reached completion, the reaction mixture was heated to 100 C. and benzyl bromide (0.7 mole, 120 gm.) was added dropwise to the stirred solution. The heat evolved by the reaction was suflicient to maintain the temperature of 100 C. for 20 minutes, after which the temperature began slowly dropping. A heating mantle was applied to the reaction flask and the temperature kept at 60 C. for one hour. The reaction mixture was then concentrated to a constant volume in vacuo; and the remaining material dissolved in 700 ml. of hexane and extracted with water until halide free. Reduction of the hexane solution to constant in vacuo volume gave 260 gm. of crude tetraisopropyl benzyl-methylenediphosphonate, C H CH[PO (OC H -i) yield 85.5%, N

Analysis.Calculated for C H O P C, 55.29; H, 8.35; P, 15.26. Found: C, 56.48; H, 8.34; P, 14.41.

In addition to the monobenzyl compound, bis-benzyl and unreacted diphosphonate in about a one to one ratio were identified.

(B) Conversion to benzyl-methylenediphosphonic acid A 72.6 gram (0.167 mole) sample of pure tetraisopropyl benzyl-methylenediphosphonate,

c m-pn crrtro 00 11 -9 1 was dissolved in 500 ml. of concentrated hydrochloric acid and refluxed for four hours. The reaction mixture was reduced to a constant volume on a flash evaporator and the last traces of water and HCl were removed by adding three portions of 2-propanol and reducing the M.P. 210 C.-212 C., yield 98.2%.

Analysis.-Calculated for C H O P C, 36.11, H, 4.55, P,23.28. Found: C, 36.20; H, 4.66; P, 23.5.

EXAMPLE II (A) Preparation of tetraisopropyl Z-carbethoxyethylidenediphosphonate A sodium dispersion was prepared by dispersing 22.99 grams (1 mole) of sodium in boiling toluene contained in a one liter, three neck flask fitted with a thermometer, a high speed stirrer, a 50 ml. offset additive t-ype separatory funnel, and an Allihn condenser. A Dry Ice bath was employed to maintain the temperatures in the desired range during the reaction. After the dispersion was cooled to 25 'C., 344.33 grams (1 mole) of tetraisopropyl methylenediphosphonate CH [PO (OC H7-i) was added dropwise to the reaction vessel over a 45 minute period, keeping the reaction temperature at 20 C.-30 C. by partial immersion of the reaction flask in the Dry Ice bath.

mixture was heated to 60 C. for one hour. The solvent,

was then removed under vacuum and the residue dissolved in 600 ml. of hexane and extracted with water until the water extract was halide free. The hexane solution was dried with anhydrous MgSO concentrated, and then distilled to give 86 grams of the tetraisopropyl 2-carbethoxyethylidenediphosphonate,

N 1.4388, yield 20%. Analysin-Calculated for C H O P C, 47.4; H, 8.4; P, 14.4. Found: C, 47.2; H, 8.7; P, 14.0.

In addition to the mono-carboxy compound, bis-carboxy and unreacted disphosphonate in about a one to one ratio were identified.

(B) Conversion to (carboxymethyl)- methylenediphosphonic acid A 43 gram sample (0.1 mole) of tetraisopropyl 2-carbethoxyethylidenediphosphonate,

was dissolved in 250 ml. of concentrated hydrochloric acid and refluxed for four hours. The resulting solution was then concentrated to a constant volume on a flash evaporator. Traces of water and HCl were removed by adding two ml. portions of 2-propanol and concentrated after each addition. A total of 23.1 grams (98.4% yield) of colorless, glassy material which had the theoretically correct p and proton nuclear magnetic resonance spectra for (carboxymethyl)-methylenediphosphonic acid was obtained; but standing in a vacuum desiccator did not produce 'a crystalline product.

Analysis.Calculated for C H O P C, 15.4; H, 3.5; P, 26.5. Found: C, 15.8; H, 3.8; P, 263.

Each of the acids prepared above are very easily converted to a salt form by reacting with a base such as sodium hydroxide. The resulting compounds perform as excellent detergency' builder materials as mentioned previously and also as exemplified hereinafter.

Valuable detergent compositions can consist essentially of a detergent compound and, as a builder, a water soluble salt of one of the new compounds identified above, the ratio by weight of the builder to the detergent compound being in the range of about 1:3 to about 10:1 said composition providing in aqueous solution a pH of between about 8 to about 12. The preferred ratio of builder to saiddetergent surfactant compound is in the range of about 1:2 to about 5:1 and the optimum pH range is between 9.5 to 11.5.

Among'the organic detergent surfactant compounds which can be successfully built by compounds prepared according to this invention are anionic, nonionic, ampholytic and zwitterionic detergent surfactants, and mixtures thereof.

The anionic, nonionic, ampholytic and zwitterionic detergent can be used singly or in combination in the practice of the present invention.

The foregoing organic synthetic detergent compounds and the novel builder compounds of this invention can be formulated according to any of the several commercially desirable composition forms, for example, granular, flake, liquid and tablet form.

The usefulness of the compounds described herein as builders can be seen from the following evaluations in which soiled fabrics were washed with detergent compositions consisting solely of a detergent and a builder.

New cotton cloth was desized, then extracted with the chloroform-methanol azeotrope. The cloth was then cut into strips five by fifteen inches, and two such strips were afiiXed to the inside of a T-shirt which was then worn by a subject for two days.'The soiled strips were then cut into 2 /2 inch square swatches and randomly mixed. The swatches were then washed in hard water (seven grains/ U.S. gal.) with 0.03% detergent concentration. Two evaluations with different detergents were run using sodium l tetrapropylene benzene sulfonate (ABS) at 140 F., and B-(dimethyl hexadecyl ammonio) propane-1- sulfonate (C APS) at 80 F. The representative members of the new compounds described herein were evaluated as builders; namely, trisodium 'benzyl-methylene diphosphonate and tetrasodium-(carboxymethyl)-methylenediphosphonate. Comparisons were made to the Widely used commercial builder, sodium tripolyphosphate (STP). After being washed in an agitator-type washing machine for ten minutes, the swatches were rinsed twice for two minutes, dried, and extracted once again with the chloroform-methanol azeotrope. The lipid extracted was compared to that in control swatches in terms of Percent Lipid Soil Removed. The results are summarized in Table II.

TABLE II Percent lipid removal ABS CmAPS (pH=10) (pH=11) Builder concentation in the wash solution Trisodium benzyl-methylene diphosphonate Sodium tripolyphosphate (0.06%)

- It is noted that the compounds'of the present. invention are on a par with the recognized standard builder.

It is also to be noted that their performance can be favorably compared to a standard builder (STP) at twice their concentration.

The foregoing description of the invention has been presented describing certain operable and, preferred embodiments. It 'is not intended that the invention should be so limited since variations and modifications thereof will be obvious to those-skilled in the art, all of Which are within the spirit and scope of this invention. 1 A

What is claimed is:

1. An alkali metal salt phosphonic acid.

References Cited UNITED STATES PATENTS 2,765,279 10/1956 Nusslein 260 500 3,093,672 6/1963 Miller 26o 932 3,159,581 12/1964 Diehl 2605 00 3,214,454 10/1965 Blaser et a1. 260500 3,256,370 6/1966 Fitch etal. 260 500 FOREIGN PATENTS 889,670 2/1962 Great Britain.

OTHER REFERENCES Freedman et al., Chem. Rev., vol. 57 (1957), p. 513. Pudovik, Chem. Abstr., vol. 47, (1953), col. 10467.

BERNARD HELFIN, Primary Examiner.

J. E. EVANS, Assistant Examiner.

of bis-(benzyl) methylenedi 

